The present invention is directed to a night vision device, and particularly to a night vision device which avoids problems caused by reflection of bright lights which may be in the field of view.
Night vision devices are well known electro-optical devices which afford a user enhanced visibility in darkness. They find widespread application in the military, law enforcement, and security operations.
A night vision device typically includes an objective lens assembly, an image intensifier tube and an eyepiece or ocular. In operation, the objective lens assembly focuses low levels of light including infrared (IR) onto the image intensifier tube, which amplifies the light and transmits it to the eyepiece for viewing of an image. The image intensifier is typically comprised of a cathode for converting light including IR to electrons, a microchannel plate for multiplying the electrons, and a phosphor screen.
A problem occurs when bright light is either in or near the field of view. Such light may bounce back and forth between the image tube and objective lenses creating xe2x80x9cghostxe2x80x9d like patterns. The stray light patterns are superimposed upon the image, obscuring the image and degrading the performance of the device.
It is therefore an object of the present invention to reduce stray light and xe2x80x9cghostxe2x80x9d like patterns caused by bright lights in or near the field of view of a night vision device.
In accordance with a first aspect of the invention, the above object is accomplished by providing an image intensifier tube having a cathode window which bears an antireflection coating.
In accordance with a second aspect of the invention, the antireflection coating is disposed on a glass plate which is adhered to the cathode window.
In accordance with a further aspect of the invention, the antireflection coating may be employed directly on the cathode window.
In accordance with a still further aspect of the invention, a laser reflecting coating may be employed on the cathode window in addition to or instead of the antireflection coating, either disposed on a plate or on the cathode window itself.